198 



THE PROTOZOA 



scopic grains of sand, or other ma- 

 terials. In some forms the skeleton is 

 internal, and may be made of lime 

 which the animals take out of the 

 water. Still other Protozoa construct 

 shells which house them for a time ; 

 then, growing larger, they add more 

 chambers to their shell, forming ul- 

 timately a covering of great beauty. 

 These shells or skeletons of Protozoa, 

 falling to the sea bottom, cover the 

 ocean floor to a depth of several feet 

 in places. 



The Protozoa have also played an 

 important part in rock building. The 

 chalk beds of Kansas and other chalk 

 formations are made up to a large ex- 

 tent of the tiny skeletons of Protozoa, called Foraminifera. Some lime- 

 stone rocks are also composed in large part of such skeletons. 



Skeleton of a radiolarian. Highly 

 magnified. From model at Amer- 

 ican Museum of Natural History. 



CLASSIFICATION OF PROTOZOA 



The following are the principal classes of Protozoa, examples of which we have 



seen or read about : 



CLASS I. Rhizopoda (Gk.= root-footed). Having no fixed form, with pseudopodia. 

 Either naked as Amoeba or building limy (Foraminifera) or glasslike skeletons 

 (Radiolarid) . 



CLASS II. Infusoria (in infusions). Usually active ciliated Protozoa. Examples, 

 Paramoecium, Vorticella. 



CLASS III. Sporozoa (spore animals). Usually parasitic and nonactive. Exam- 

 ple, Plasmodium malarice. 



REFERENCE BOOKS 



ELEMENTARY 



Sharpe, A Laboratory Manual for the Solution of Problems in Biology. American 



Book Company. 



Davison, The Human Body and Health, Chap. XXIV. American Book Company. 

 Davison, Practical Zoology, pages 178-184. American Book Company. 

 Jordan, Kellogg, and Heath, Animal Studies. D. Appleton and Company. 

 Ritchie, Human Physiology, Chap. XXVI. World Book Company. 



ADVANCED 



Calkins, G. N., The Protozoa. The Macmillan Company. 



Linville and Kelly, General Zoology, Chap. XXI. Ginn and Company. 



Parker, T. J., Lessons in Elementary -Biology. The Macmillan Company. 



Seaman, L. S., "The Sleeping Sickness," Outlook, Jan. 15, 1910. 



Wilson, E. B., The Cell in Development and Inheritance. The Macmillan Company. 



